1. Field of the Invention
The present invention relates to a pattern-forming method and a resist underlayer film-forming composition.
2. Discussion of the Background
An integrated circuit device has been produced using a multilayer resist process that implements a reduction in pattern size in order to achieve a higher degree of integration. When using the multilayer resist process, a liquid resist underlayer film-forming composition and a liquid photoresist composition are sequentially applied to a substrate. A mask pattern is transferred to the photoresist film using a reduction projection aligner (stepper), and the photoresist film is developed using an appropriate developer to obtain a photoresist pattern. The photoresist pattern is transferred to the resist underlayer film by dry-etching. The pattern of the resist underlayer film is transferred to the substrate by dry-etching to obtain a substrate having a desired pattern. A multilayer resist process that utilizes one resist underlayer film may be referred to as “two-layer resist process”, and a multilayer resist process that utilizes two resist underlayer films may be referred to as “three-layer resist process”.
The resist underlayer film normally functions as an antireflective film that absorbs radiation reflected by the substrate. The resist underlayer film that comes in direct contact with the substrate is normally formed using a material having a high carbon content. The etching selectivity when processing the substrate is improved when the material for forming the resist underlayer film has a high carbon content, so that the pattern can be transferred more accurately. A thermosetting phenol novolac resin is well-known as the material for forming the resist underlayer film. It has been known that a resist underlayer film formed using a composition that contains an acenaphthylene polymer exhibits good properties, for example in JP-A 2000-143937 and JP-A 2001-40293.
However, the resist underlayer film may be over-etched when further reducing the size of the etching pattern. Therefore, an improvement in pattern transfer capability and etching resistance has been desired. In particular, it has been desired to prevent a situation in which the pattern of the resist underlayer film is bent when transferring a fine pattern using the resist underlayer film as a photomask.